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ALUMINIUM                                         273

metals determined as in the case of ordinary brasses when manganese is
absent, or like complex brasses when manganese is present.1

B. IN PRESENCE OF NICKEL. In this case, the preliminary removal of
the nickel as nickeloxime is necessary*. When the metal is attacked as
described above, the liquid is filtered to remove the suspended carbon and
silica, these being washed and the filtrate treated with ammonia until the
copious precipitate first forming redissolves. The last clots of precipitate
are dissolved by heating on a water-bath and the clear liquid treated with
i% alcoholic dimethylglyoxime solution in slight excess. After a short
stand on a water-bath the precipitate is collected in a Gooch crucible, washed
firstly with hot water containing a little ammonia and ammonium tartrate
and then with hot water alone until the filtrate is neutral, dried at 120°
and weighed : nickeloxime X 0-2032 — nickel.

The filtrate is heated on a water-bath to expel the alcohol and then
treated with just sufficient hydrogen sulphide to precipitate the metals in
solution, the subsequent procedure being as in A (above).

2.  Determination of the Tin.—The sodium or ammonium sulphide
solution in the 300 or 500 c.c. flask is made up to volume and an aliquot
part (100 or 150 c.c.) treated, in a f-Iitre flask covered with a small funnel,
with small quantities of hydrochloric acid and with shaking until the re-
action is acid.    A further quantity of 25-30 c.c. of cone, hydrochloric acid
is added and the liquid boiled, if necessary with addition of a few crystals
of potassium chlorate, until the tin sulphide at first separating redissolves
in the excess of hydrochloric acid.

The solution is then treated with 25-30 grams of ammonium oxalate
and electrolysed at 50-60° to determine the tin (see Electrolytic Determina-
tion of Tin in Ordinary Bronzes).

3.  Determination of the Carbon.—This is carried out directly on a
portion of the sample by either the Corleis method or the copper chloride
method (see Determination of Total Carbon in Iron).

4.  Determination of the Silicon.2—i  gram   of  the  aluminium  in
small fragments is dissolved in 300 c.c. of a mixture of 100 c.c. of nitric
acid (D 1-42), 300 c.c. of hydrochloric acid (D 1-2) and 600 c.c. of 25%
sulphuric acid.    When the action comes to an end, the liquid is heated
carefully on a sand-bath until abundant white sulphuric acid fumes appear.
When cold the residue is taken up with water acidified with sulphuric acid,
heated to dissolve the aluminium sulphate and filtered, the vessel and filter
being washed first with water acidified with sulphuric acid and then with
water alone.3   The residue on the filter, consisting of silica, graphitic silicon
and a little alumina, is dried, ignited and fused with sodium carbonate, the
cold mass being dissolved in water acidified with hydrochloric acid and
evaporated to dryness ; this treatment with hydrochloric acid is repeated
several times and the residue finally heated in an oven at 135° to render
the silica completely insoluble (see Iron, 2).

1 Any cobalt present is determined electrolytically under the conditions indicated
for the determination of the nickel.

2 According to I. O. Handy: Journ. Amer. Chem, Soc., XVIII, p. 736.

3 In presence of lead, the washing is carried out first with hydrochloric acid (D 1-2)
and then with water, as usual.

A.C.                                                                                                      18 if the metal is 'er of these methods is washed with water, alcohol and ether, dried at